From BBC Earth's Arj Singh:
As we approach winter, the nights start drawing in and the days become darker, it seems like the perfect time of year to celebrate light.
That's what happens during the religious festivals of Hanukkah and Diwali and we at BBC Earth wanted to have a celebration of our own.
We've turned to the beauty of light in nature for inspiration, and picked some of our favorite bioluminescent animals.
These strange, wonderful and rare creatures actually emit light. Whether it's from 'fishing rods' coming out of their heads or from squirted protective 'ink', the phenomenon certainly brightens up our days...
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These weird predators look more like something you’d find in a novelty electrical store than planktonic ocean life but they are one of the most amazing examples of bioluminescence. Sea gooseberries use their two long, trailing tentacles to fish for prey. Their bodies are virtually transparent and rows of tiny cilia catch the light, producing rainbow-like colors and turning the waves into ocean rainbows. Made up of 99 percent water, these comb jellies still manage to feed on other plankton.
These funny-looking creatures get their name from their ear-like fins that resemble the famous flying elephant. Living deeper than almost any other octopus, these animals exhibit bioluminescence, although not much is known about why. The largest dumbo octopus ever found was six feet long and weighed 13 pounds. But living at depths of up to 22,000 feet, it’s hard to tell how big some could be…
The polychaete worms that live in the bottom of almost unfathomable lakes like this one would be one of the last animals you’d think bioluminescent. That’s because they have no organs for detecting light and live their entire adult lives in buried tubes. But when disturbed, the worms move to the end of their tubes and secrete their blue light feeding mucus. That’s probably the prettiest mucus in the world!
These famously odd fish use a red light on the end of a ‘fishing rod’, or esca, on the top of their head to attract prey. But here the bioluminescence comes from bacteria that enter the esca through small pores. Here, they multiply until there are so many of them that their collective glow becomes like a light. Incredibly, male anglerfish have adapted to become entirely parasitic and will bite into a female, attaching to her skin and blood supply. Gradually they lose all their internal organs apart from their testes. A female usually carries six or more males.
This actually rather timid squid is a target for predators underneath it who see the blackest depths of the ocean like we see twilight. But the vampire squid is a clever one. It emits its own blue light in a strategy called counter illumination. This cloaks its silhouette and removes it from the sight of the watching, hungry eyes below.